Warner Bros. announced Monday what Prince fans have been waiting for since last April or maybe since 2009 — his first U.S. album in five years. “Art Official Age” will be released on Sept. 30, as will “Plectrum Electrum” by 3rdEyeGirl. “Plectrum Electrum,” which Prince had been talking about releasing last year, was made with his all-female backup band. “AOA” is essentially a solitary Prince project recorded with co-producer/musician Joshua Welton.